In a case of tires mainly for use in winter such as studless tires, on-ice performance thereof has been conventionally improved by using a rubber composition including a hydrophilic resin blended therein in tread portions of the tires. Use of a rubber composition including a hydrophilic resin blended therein in a tread portion of a tire satisfactorily ensures a good affinity of a tread surface for water on a road surface, thereby imparting the tire with good drainage properties to successfully improve on-ice performance thereof.
For example, PTL 1 discloses using a composition including a hydrophilic polymer blended therein in a tread portion of a tire and PTL 2 discloses using in a tread portion of a tire a composition including a water absorption agent obtained by introducing intermolecular crosslinks into water-soluble polymers.